A process is already known according to which oil containing seeds are heated in so-called cookers or flour boilers in the presence of moisture. Such a flour boiler is constituted as a vessel with a plurality of hollow plates disposed one over the other, each provided with a passage whose discharge opening is located over a plate situated thereunder. The oil-containing seeds are essentially indirectly heated by the plates.
In order to extract oil from oil-containing vegetable raw materials, such as fruits or seeds, by squeezing or extracting by means of solvents, it is necessary to expose these raw materials previously to a number of pre-treatments. Irrespective of the specific pre-treatments for each kind of seed and the differences due to extracting or crushing, the folowing examples of pre-treaments can be mentioned in arbitrary order of succession, i.e.: removal of shells, skins or husks, pulverizing, rolling, heating, drying and cooling.
In dependence of the raw material and the oil extraction process proper, one or more of these pre-treatments are required and some of them even simultaneously. Although the mechanisms between pre-treatment and oil extraction are not yet entirely known, the pre-treatments effectuate that:
CELL MATERIAL IS OPENED, WHEREBY THE OIL IS MORE EASILY RELEASED;
UNDESIRED COMPONENTS, SUCH AS ALBUMINS, SLIME AND THE LIKE ARE FIXED AND BECOME INSOLUBLE;
THE REST OF THE CELL WALLS ARE STRENGTHENED.
The known process suffers, however, from the disadvantage that the residence of the product in the cookers or flour boilers often exceeds the optimally necessary time, while moreover a uniform well controlled treatment of the particles is impossible. This is caused by the very poor heat conduction and heat transfer, due to the fact that in the known process the heat supply is substantially indirect, that is to say it is effected via a heat exchanging surface, while additionally, the heat conductivity of the product to be treated is very in-sufficient, since it is in the form of bulk material when exposed to the treatments.